Treating steel



Sept. 27, 1938. H M. GARssoN TREATING STEEL Filed Aug. 16, 1938 |l-f Il|1|' '11| 'Il f1 Il Ill lll en/jg M. 621/1560,

eunooleuloonuoooonao onuoaoavoonaaanono l 2 of c eaoooocneoo.onesuonunnonoaccsnorovoao seneca. ncavnuoao'oaoo amaca.. nonacononnvaanNI Patented sept. 27, 193s PATENT ori-"ICE Application August 16,

20 Claims.

instruments, and other steel articles in which a bright clean'surface ora colored surface may be desirable or where it may be desirable toremove impurities frorn the metal in order to obtain uniformity ofcomposition. While the invention is adapted for treatment of steel forvarious uses. for purposes of illustration it will be described mainlyin connection with treatment of razor blade strip, in the manufactureand treatment of which the invention is particularly desirable.

Steel employed in the manufacture of razor blades is generally producedin the form of a very thin strip cutinto the shape of a succession ofrazor blades attached at their ends. The strip, then, is substantiallythe width of the finished razor blade. For forming the strip it isdesirable that the metal be in an unhardened, readily workable conditionbut before the nal blade is produced the metal must be hardened,tempered and otherwise treated. Inasmuch as the strip is very thin itishighly important that it be free from aws and defects. It is highlydesirable that the strip be of a homogeneous character and especiallythat its surface be of a uniform character throughout the area of theblade. One reason that this is important is that if there is a lack ofuniformity portions of the surface may break away or stains, defects orimperfections may appear in the surface. It is highly important not onlythat the razor blade be of homogeneous character but also that itssurface have a pleasing, uniform appearance to aid in its sale byappealing tothe purchasing public. The thinner the blade the morenecessary is homogeneousness in the make-up of the steel. Likewise thethinner the blade. the more desirable it is that impurities orimperfections not entirely confined thereto it is a purpose of thepresent invention to treat strips for the manufacture of blades ofunusual thinness, that is, thinner than the majority of blades now onadapted for cutlery including knives and surgical may be removed oreliminated or avoided. While TREATING STEEL Henry M. Gannon, FarRockaway, N. Y.

1938, Serial No. 225,121

the market. An important attribute of a razor blade is the possibilityof flexing or bending to fit neatly and accurately into the-razor bladeholder when adjusted to suit the desires of the user. Such an unusuallythin blade especially well adapts itself to such appication.

For purposes of ornamentation, beauty, identification and attractivenessit is possible to apply a coating to the blade surface or to so treatthe blade surface that the surface layer has different metallurgicalcharacteristics from the body of the blade. Such treatment may beespecially undesirable with very thin blades. It is a purpose of thepresent invention to produce a blade of substantially uniformcharacteristics throughout its thickness and a satisfactory, pleasing,attractive surface finish or appearance.

After the blade strip has been made in the desired form it is passedthrough a heating device which raises its temperature to something morethan the critical temperature of the metal, say from 1400 C. to 1'100JC. for carbon, chrome or spring steel which is suitable for razorblades. At such temperatures it has been found that there is arearrangement of the grain formation of the metal at least to someextent but there may also be an undesirable surface effect. One phase ofthe present invention contemplates this heat treatment of the razorblade strip in a Vfurnace supplied' with an atmosphere of a reducinggas. If oxygen or moisture is present at this temperature oxidation mayresult producing a colored film of oxide on the surface of the steel.Such a film m-ay be very undesirable and unless it is absolutely regularin appearance it may give an undesirable appearance and. so be a defectfrom a sales standpoint. In order to avoid this oxidation preferably airis not permitted in the heating chamber through which the strip of steelpasses. Oxidationmay be avoided by filling the space in the heatingfurnace preferably with a reducing gas such as illuminating gas,hydrogen, carbon monoxide, methene, etc. Often in such a furnace theheating action of the razor blade strip may not be satisfactory. Evenwhen a bade looks satisfactory and approximately uniform to the nakedeye it may be found on careful examination that the apparently smoothsurface is often pitted with minute depressions. The strip of steelwhich is used for the manufacture of blades often contains imperfectionsin the form of oxides, etc., which are unaffected by the usual hardeningprocess. There are found in the hight grades oi' carbon or alloy steelsused for cutlery and razor blades certain structural features4crystallization if present be deformed so that the final structure ofthe steel in the blade is o ahmore rened order. This result of homogeneuousness in the metal may be accomplished by the introduction bf acatalytic agent in the presence of a reducing gas in the furnace wherethe heating step of the hardening process takes'lplace. If there areoxide imperfections in the steel oxygen may be liberated athightemperatures in the presencelof platinum. It is not lmown dei nitelywhen such tendency to liberation oi oxygen arises but it seems to beginat about 400 tc 600 C. and above. It is especially noticeable at l000 C.and above. The preferred catalyst 'in 'the heating chamber is platinumwhich may be in the form of pure sponge platinum or in the form of blockor strip or a platinum wire. The exact theoretical operation or effectof the platinum is not known. The platinum, however, seems to act as acatalytic agent as the temperm ature in the chamber rises and uponcontact with the platinum a very strong adsorption of C. or even as'high as 1700 C. The eiect or' oxygen is particularly undesirable. Theoxygen liberated at high temperatures from the steel or itsimperfections may normally be reabsorbed in the steel on cooling butinstead of such a. reoxidation taking place the adsorption of the oxygenon the surface of the platinum and the reducing action. due to thepresence of the platinumy catalyst results in a chemical reaction of theoxygen. A combustible gas in the presence of oxygen in a very smallproportion or viceversa will not operate completely without the presenceof a catalytic agent. The catalytic agent preferably used for thispurpose is either a glowing platinum wire, pure platinum sponge or solidplatinum which acts upon contact. The result upon the steel when no airor oxygen is present but the platinum catalyst is present is` to producea brighter nish and an improved or greater degree of uniformity inregardto the hardness and granular arrangement of the steel.

i Although ordinarily the presence of an oxide on the surface of theblade strip may be detrimental it may be desired to color the blade byproducing an oxide. When a coating is provided for the blade it is apurpose of the present invenais-.ipse

'The usual scheme now used for chilling contemof the furnace not in acontinuous movement polishedcrystal magnetite but displaying color dueto the oxide. The color may be a. deep blue, purple or the like,depending upon the temperature and the character of the gas present.Even ii oxide should be formed by oxygen being present the presence ofthe catalytic platinum improves considerably the quality of the steel.It seems to insure an even dispersion of the surface oxide andsubstantially eliminates the tendency ci the oxide to pull away from themetal on which it is formed. From such a tendency results an unevenhardness which may, in part at least, be due to the variation inthermo-conductivity of the oxide and of the steel.

When it is desired to produce or provide a coating or surface on theblade by oxidizing there may be introduced into the furnace' containingthe platinum catalyst atmospheric air or treated or ozonated air whichmay be produced by any of the Well known ways of treating air' to enrichor change itsoxygen content before it is passed into the furnace. Thetheoretical effect of the oxygen is not thoroughly understood. Theeffect of the ozonated air, that is air containing ozone, may be that byits more rapid action in forming the oxide surface or coating it has abeneiicial edect on the metal. It is noted that the operation in thepresence of 'the platinum catalyst substantially avoids or eliminatesthe scaling which usually occurs when rapid oxidation takes place kandleaves a smooth, polished surface on the blade strip the color of whichvaries generally with the temperature to which the blade strip issubjected in the furnace.

The effect of the presence of the platinum catalyst is also further toimprove -the quality of the strip steel during the process of hardening.The integrity or uniformity of the metal is better than that produced bythe usual process employed in the manufacture of such strip steel. Thereis substantially no irregularity of thermo-conductivity throughout anindividual blade made by the process here described.

After the razor blade strip has been raised to the critical temperaturein the presence of the platinum catalyst and the structure rearranged itis necessary that the uniform arrangement of the steel be made permanentby sudden chilling.

plates conveying the blade strip continuously from the heating furnacepast, over or through a cooling element. It is clear that in such anarrangement the leading end of a single blade will be introduced intothe cooling device prior to the hind end of the blade in the strip. Thusduring the time required for a single blade unit to be chilled therewill be a continuous variation or divergence of temperature in the bladeunit. This may tend to produce irregularities during the chilling. It isa. purpose of the present invention to avoid this possibility ofproducing lrregularity by passing the strip through and out with thestrip or so that the strip is more or less 'I out of their influence.While.l the blocks remain thus the. strip is led forward and withdrawnfrom the furnace the length of a blade unit. During this time the stripis not strongly influenced by the cooling blocks. The movement of thestrip is then discontinued and while the blade unit remains immovablethe chilled cooling blocks are caused to approach the furnace exitandenclose and suddenly chill the blade unit. As soon as the blocks arecooled and are brought together to influence the strip the blade unit asa whole will be cooled and this variation in temperature within theindividual unit may tend to be avoided. The stopping of the strip needbe only momentary sincethe blade is very thin and will be readily andpromptly chilled. Preferably the strip will beJI suddenly chilled fromthe temperature of approximately 1400 C. in the furnace'to about 40 C.to 60 C. The chilling blocks may conveniently be kept at about thistemperature by passing through them water or other chilled materials.While this sudden chilling of the blade -unit may be suilicient to putthe strip in proper condition it is preferred to have additionalchilling blocks adjacent the moving chilling blocks. Inasmuch as themovable enclosing chilling blocks will'bring the strip to a lowtemperature the additional chilling blocks need not be movable but thestrip may be passed between them for further chilling to substantiallyatmospheric temperature or below. These additional chilling blocks alsoact as guides for the strip and they may also prevent curling orphysical deformation of the strip which might otherwise occur. By theuse of the chilling blocks a substantially constant final temperature ofthe strip is insured, thus substantially eliminating the possibility ofirregularities' or defects occurring in the strip after it has left thechilling blocks. The chilling apparatus may preferably be enclosed in achamber where no oxygen is present. It may be convenient, therefore, toenclose the chilling blocks in a chamber lled with a reducing gas of thecharacter heretofore referred to.

The chilling blocks may be brought to the desired temperature by any.suitable means. Thus water from a well or the city mains may be employedor previously cooed or refrigerated water or other suitable material maybe used in the .cooling blocks or for the purpose of cooling them.

As the strip comes from the cooling blocks after the hardening it willordinarily be extremely hard and it will also be very brittle. In thiscondltionit is not suitable for ordinary use as razor blades It isimportant that the blade acquire a proper combination of hardness andelasticity. This may be accomplished by a tempering process which mayconveniently take Y emerging from the tempering chamber the strip ispermitted to cool to atmospheric' temperature without `being suddenlychilled. By proper adjustment of temperature, which according to the @teof speed at which the strip passes through the furnace may range fromabout 300 C. 500 C., the treatment will result in imparting aspringiness to the blade which permits it to conform to the shape of therazor or blade holder and to suitably and sa'tisfactorly perform itsshaving function. The particular purpose of this part of the process isto relieve any strains in the metal which may be present after thehardening and to produce uniformity of solidness and optimum elasticityand flexibility. During this process as ordinarily carried out manytimes a yellowish oxide is formed on the blade which must be eitherpolished oif or will spoil the blade to such an extent as to require itsrejection upon inspection. During the tempering if there is more thanthe usual amount of humidity or moisture in the air some oxidation maytake place. The oxidation ordinarily mayl not.-cover the blade entirelywith the lm of oxide but may result in imperfection and discoloration orspottiness. In order to avoid this and to produce a blade strip ofuniform condition and appearance it is preferred `to place in thetempering chamberplatinum which may be pure platinum sponge, or solidplatinum, or a platinum wire. Both in the tempering chamber and in thehardening chamber above described the platinum present may be brought toa glow or to incandescence or other suitable temperature by passing anelectric current through it. This may be especially important in thetempering chamber in which the temperature is only 300 C. to 500 C. atwhich temperatures platinum ordinarily will not be incandescent. Thetempering chamber in which the platinum is installed may preferably beprovided with a nonoxldizing atmosphere. To this end the temperingchamber may be filled with a reducing gas such as referred to above.When such a tempering chamber is used there will' be imparted to thetempered blade strip a bright silvery nish. The surface of the bladethus produced may be somewhat similar to the finish applied to silverarticles and generally referred to by jewelers as the platinum finish.This is a soft silvery texture which ordinarily persists until the bladeis used and gives to the blade an especially attractive appearance whichmay be satisfactory and attractive `to the purchaser and user of thefinished blade. In the heating chamber the platinum apparently acts as-acatalyst. The theoretical or scientific explanation of the -result maynot be known but apparently .while possible imperfections by reason ofoxidation are avoided, reducing action von the oxides due to thepresence of the platinum catalyst in the reducing gas atmosphere in theheating chamber thoroughly cleans the surface and insures a uniformtempering throughout the blade. The effect of theentire process is toproduce a better cutting edge and a more resilient blade.

Even when the blade strip is not hardened in the way above described animproved effect is produced by tempering in the way above described.'Ihe employment of the entire process above outlined or portions of itwill tend to produce a uniform condition in the razor blade whether theblade is colored or not-` and whether or not the reducing gas isemployed in one or both chambers. Even ywhen the reducing gas is notpresent the employment of the platinum catalyst is desirable andadvantageous although its best effect maybe produced in the reducingatmosphere.

Similar operations and eflects may be employed and observed inconnectionl with the in vention as adapted to steel used .for purposesother than. razor blades. The units to be used may be marked orindicated Kon the strip or it may be cut into proper'un'its and putthrough the treatment on a conveyor.

The invention is not confined to the use of any specific form ofapparatus but as an example one specic form of apparatus especiallyadapted for the treatment of razor blade strip is illustrated in theaccompanying drawing in which' Figure la and Figure lb togetherillustrate a sectional view in a diagrammatic way of one speciflc-formof apparatus which may be employed for carrying out the invention. Fig.2 is a transverse vertical section of a pair of cooling blocksillustrated in the closed position. Fig. 3 is a plan view of a fragmentof one form of razor` blade strip.

The razor blade strip I8 having been reduced to the outlinesubstantially as indicated in Fig.` 3 is introduced in any suitable wayinto the furnace ii where it may be treated for hardening. The furnaceil is illustrated as an ordinary type of electric furnace provided withexternal insulation i2 ,surrounding heating coils i3 which surround theheating chamber I4. A pipe I5 provided with an outlet valve i6 isillustrated for introducing into the chamber i4 a suitable gas whichpreferably will be a reducinggas. The ends of the furnace II aresubstantially closed leaving only a small slot for the entrance andegress` ofthe razor blade strip l0. At a suitable place in the chamberI4 of the furnace may be arranged platinum in suitable form such assponge platinum, block platinum or platinum wire. In the drawing isillustrated a platinum bar |1 suitably supported at about the center ofthe furnace II although this is not essential. In order to allow thegases to come in contact with as much of the platinum surface aspossible it is desirable that the platinum bar |1 be mounted freely inthe air or be supported by porous or brick work blocks I8. Thetemperature of the furnace will be kept at slightly above the criticaltemperature of the steel being employed say from 1400 C. to 1700 C.Preferably a very thin razor blade strip I0 will be employed'in thefurnace Il and it has been found that when strip'is raised to thetemperature indicated it will sag and may break if a considerablestretch of it is left unsupported. Ordinarily the free portion of thestrip should not be over about 8 inches and for this reason there areindicated in the drawing supporting members I9 positioned relative tothe,platinum block I1 to leave never morethan seven or eight inches ofthe blade strip hanging free. The blade strip passes through the heatingfurnace I| and as it leaves the furnace passes between the upper movablecooling block illustrated at 20 and thev lower movable cooling blockillustrated at 2 I. The cooling blocks are diagrammatically illustratedas mounted to slide in a vertical guideway 22. Lever arms 23 connectedto the movable blocks 2| and 22 at their other ends are pivoted to abearing 24 sliding in a horizontal guideway 25. Connected to the bearing24 is an arm 26 which is .moved by suitable power driving gearing 51 insuch a way as to reciprocate the bearingmember 24. As this reciprocates4it causes the blocks 20 and 2| to separate andto again approach eachcother. Mounted beyond the movable cooling blocks 20 and 2| areillustrated stationary cooling blocks 21 which may be of any suitablesize and number. The cooling block groups are shown as longitudinallyseparated but they may be in close contact with each other and with themovable blocks 28 and 2|. Driven by the gearing 51 is a preferablyforked arm 28 which may be caused to rise and engageA the razor bladestrip at opposite marginal apertures 29 so as to grasp the blade stripI0 and pull it through and out of the furnace I. The arm'28 will give anintermittent movement to the blade strip ID and this is arranged incooperation with the arm 2G so that the movable cooling blocks 20 and 2|are separated during the period the arm 28 imparts movement to the razorblade strip. The arm 28 is then freed of the razor blade strip whichremains unmoved during the time the arm 25 brings the cooling blocks 2Uand 2| together to chill the portion of the blade strip between them.The device preferably s so arranged that the arm 28 moves the razorblade strip at each step the length of a single blade unit as indicatedbetween the marginal apertures 29. This is desirable so as to producethe desired sudden Vchilling; uniformly throughout each blade unit asindicated above. The arm 28 may be so adjusted and operated as to movethe strip a distance equal to the length oi' a plurality of razor bladeunits and likewise the cooling blocks 28 and 2| may be made of anysuitable length but preferably will be of a length equal to the lengthof.a single razor blade unit or of a plurality of razor blade units. Thearm 28 pulls `the razor blade strip I0 through the furnace and thecooling blocks 20, 2| and 21 and forces the strip into and through thetempering furnace 59. While not essential the tempering furnace is hereillustrated as oi' the electric furnace type having a central chamber 30through which the razor blade strip passes to be heated and throughwhich it emerges to be cooled slowly and preferably wound Iupon a roller3| for convenience in further handling. The roller 3| may rotatecontinuously and between it and the furnace 59 may be n provided a.roller 32 forced by a spring 33 against the razor blade strip IU to takeup slack due to the fact that the razor blade strip is movedintermittently or step by step while the roller 3| is rotatedcontinuously.- In the chamber 38 of the furnace 59 will preferably beinstalled platinpm in the form of pure sponge platinum, solid platinumor platinum wire. For purposes of illustration there is illustrated aplatinum wire 34 unsuppported and stretching from end to end of thefurnace 59. The platinum wire 34 like the platinum bar I1 may be heatedby bringing to incandescence or any suitable temperature by passing anelectric current throughit.O This maybe particularly important inconnection with the furnace 59 where the temperature is maintained inthe chamber at only about 400 C. A pipe 35 A controlled by a valve 38may be provided to supply the chamber 30 with a reducing gas of thecharacter above indicated.

1- In Fig. 2 the movable blocks 20 and 2| are shown in their closedposition in which they enclose and nearly contact the razor blade stripI8. In these' Ablocks as in the blocks 21 pipes may be employed for theingress and egress of cooling liquid. The pipes 31 may be of flexiblematerial such as rubber so as to allow the cooling blocks 20 and 2| tobe moved.

It may be desirable to effect the chilling in the absence of oxygen orair. To this end a casing 38 may be arranged about the chilling blocks28, 2| and 21 and the interior of the casing 38 may be supplied with aninert gas or a reducing gasof the character indicated. For this purposethere is indicated a pipe '39 provided with a valve. 40 through whichthe gas may be passed to the interior of the casing 38.

It may be desirable to partially reduce the temperature of the bladestrip before it exits from the tempering chamber 30. For this purposethere may be used a plurality of heating coils in the furnace 59. Twoheating coil units 4I and 42 are indicated. If desired the heating coil4| for instance may be maintained at the tempering temperature ofapproximately 400 C. while the heating coil 42 may be maintained at asomewhat lower temperature, say 250 C. Any suitable muiile 43 may beemployed for separating the coils 4| and 42.

The invention has been described as applied to a strip of connected.blade blanks or other articles but it is not limited to such a strip.The blanks for individual blades or other articles may be severed andcarried by a conveyor through the treating mechanism. The term razorblade strip or steel strip is here used as broad enough to include oneblade or other unit'or more than one blade or other unit whetherphysically connected together or arranged on a conveyor and irrespectivelof the character or form of the unit.

The invention has been described in much detail but all phases describedare not essential to the successful production of a satisfactory razorblade and obviously the invention is not confined to all of the specificdetails herein referred to.

This case is a continuation in part of application Ser. No.\135,599,filed Apr. 7, 193'7.`

I claim as my invention:

1. The method of treating steel strip comprising placing in a chamberplatinum to act as a catalyst,'heating the chamber to above the lowercritical temperature of the strip, keeping the chamber lled with areducing gas, feeding the strip through the chamber to cause itsmolecules to be rearranged and included oxygen to be re-`v moved, movingthe strip from the chamber by la step by step movement and betweencooling blocks which separate during the movement of the strip andcomevtogether to substantially engage the strip while it is stationary,Passing the strip between additional immovable cooling blocks, feedingto the cooling blocks a cooling medium at about 40 C. to 60 C.temperature, from the cooling blocks passing `the strip to a temperingfurnaceymaintaining the furnace at about 400 C., maintaining heatedplatinum in the tempering furnace as a catalyst, keeping the temperingfurnace filled with a reducing gas, and removing the strip from thetempering furnace and slowly cooling it to atmospheric temperature.

2. In the method of treating steel strip divided into units to produce auniform texture the steps of heating the strip to above its lowercritical temperature, and cooling a part onlyv of the' strip by4suddenly applying cooling means to an entire integer at least as largeas a single unit.

3.. The method of treating steel strip comprising placing in a chamberplatinum to act as a at about 400 C., maintaining heated platinum `inthe tempering furnace as a catalyst, and removing the strip from thetempering furnace and slowly cooling it to atmospheric temperature.

4. The method of treating steel strip comprising heating a chamber toabove the lower critical temperature of the strip, feeding the stripthrough the chamber to cause its molecules to be' rearranged andincluded oxygen to be removed, moving the strip from the chamber tocooling blocks at about 40 C. to 60 C. temperature, from the coolingblocks passing the strip to a tempering furnace, maintaining the furnaceat about 400 C., maintaining heated platinum in the tempering furnace asa catalyst, keeping the tempering furnace filled with a reducing gas,and removing the strip from the tempering furnace and slowly cooling itto atmospheric temperature.

5. The method of treating steel strip comprising heating a chamber toabove the lower critical temperature of the strip, feeding the stripthrough the.chamber to cause its molecules to be rearranged and includedoxygen to be removed, moving the strip from the chamber by a step bystep movement and between cooling blocks which separate during themovement of the strip and come together to substantially engage thestrip while it is stationary, passing the strip between additionalimmovable cooling blocks, feeding to the cooling blocks a cooling mediumat about 40 C. to C. temperature, from the cooling blocks passing thestrip to a tempering furnace, maintaining the furnace at about400 C.,maintaining heated platinum in the tempering furnace as a catalyst,keeping the tempering furnace filled with a reducing gas, and removingthe strip from the tempering furnace and slowly cooling it toatmospheric temperature.

6. The method of treating steel strip comprising heating a chamber toabove the lower critical temperature of the strip, keeping the chamberfilled with a reducing gas, feeding the strip through the chamber tocause its molecules to be rearranged and included oxygen to be removed,moving the strip from the chamber by a step by step movement and betweencooling blocks which separate during the movement of the strip and cometogether to substantially engage the strip while it is stationary,passing the strip beween additional immovable cooling blocks, feeding tothe cooling blocks a cooling medium at about 40 C. to 60 C. temperature,from the cooling blocks passing the strip to a tempering furnace,maintaining the furnace at about 400 C., and removing the strip from thetempering furnace and slowly cooling it to atmospheric temperature.

7. The method of treating razor blade strip marked into individualblades comprising producing a smooth shiny surface and a uniform textureby heating the strip to above its lower critical temperature in thepresence of a reducing gas and a platinum catalyst, cooling the stripsuddenly in integers at least as large as a single blade, heating thestrip to a tempering temperature in the presence of a reducing gas and aheated platinum catalyst, and slowly bringing the strip to aboutatmospheric temperature.

8. The method of treating steel strip comprising producing a smoothshiny surface and a uniform texture by heating the strip to above itslower critical temperature in the presence of a reducing gas and aplatinum catalyst, cooling the strip suddenly, heating the strip to atempering temperature in the presence of a reducing gas and a heatedplatinum catalyst. and slowly bring- 'ing the strip to about atmospherictemperature.

9. The method of treating steel strip marked into units comprisingproducing a smooth shiny surface and a uniform texture by heating thestrip to above its lower critical temperature in the presence oi areducing gas and a platinum catalyst, cooling the strip suddenly inintegers at least as large as a single unit, heating the strip to atempering temperature, and slowly bringing lthe strip to aboutatmospheric temperature.

l0. The method of treating steel strip comprising producing a smoothshiny surface' and a uniform texture by heating the strip to above itslower critical temperature in the presence of a reducing gas and aplatinum catalyst, cooling the strip suddenly, heating the strip to atempering temperature, and slowly bringing the strip to aboutatmospheric temperature.

11. The method of treating steel strip comprising producing a smoothshiny surface and a uniform texture by heating the stripto above itslower critical temperature, cooling the strip suddenly, heating thestrip to a tempering temperature in the presence of a reducing gas and aheated platinum catalyst, and slowly bringing the strip to aboutatmospheric temperature.

l2. The method of treating razor blade strip marked into individualblades comprisingl producing a smooth shiny surface and a uniformtexture by heating the strip to above its lower critical temperature,cooling a part only of the,

strip by suddenly applying cooling means to an l entire integer at leastas large as a single blade.

heating the strip to a tempering temperature, and slowly bringing thestrip to about atmospheric temperature.

heating it to about 300 C. to 500 C. in the presence of incandescentplatinum in a reducing gas. i7. In treating steel strip, the stepcomprising heating it to about'its critical temperature in the presenceof incandescent platinum and an oxyrlizingggagent.

i8. In treatingsteel strip, the step comprising heating it to aboutits'critical temperature in the presence of incandescent platinum in anatmosphere containing ozone.

i9. ln treating steel strip, the step comprising heating it to about itscritical temperature in the presence of incandescent platinum in anatmosobere containing a reducing gas and an oxidizing gas.

20. in they method of treating razor blade strip divided into individualblades to produce a uniiorm texture the steps of heating the strip toabove its lower critical temperature, and cooling a part only of thestrip by suddenly applying cooling means to an entire integer at leastas large as a single blade.

HENRY' M. GARSSON.

